A ceramic insulator is the most important component in a ceramic metal packaging outer shell, and is widely used in the photo-electronic communication field. Regarding to a ceramic insulator with a step-shaped double-deck bonding pad structure, an upper layer of the ceramic insulator is an electric control layer, a lower layer of the ceramic insulator is a RF (Radio Frequency) layer, and both the upper and lower layers need to be coated with nickel-gold protection layers so as to enhance the reliability of their structures and electrical properties.
Currently, there are two methods for coating metal onto a ceramic insulator with the aforesaid structure: 1) after coating of a nickel layer on exposed metal parts of a porcelain (ceramic) is realized by a chemical deposition method, the porcelain (ceramic) is assembled with metal components by brazing; afterwards, the disconnected circuits are connected to be conductive by a gold wire ball welding bonding wire method, and then nickel-gold electroplating is performed; after coating of a nickel-gold layer is entirely finished, metal strips are shoveled off; 2) no bonding wire is formed, and the coating of the nickel-gold layer is realized by a chemical coating method.
However, after the electroplating is realized by the connection using the bonding wires, the metal strips need to be shoveled; thus, it is inevitable to remain shoveling traces on the circuits, and thereby affect appearance and reliability of the porcelain (ceramic). In addition, compared with the electroplating method, the adoption of the chemical coating method may result in relatively lower coating layer density and bonding strength, and can't meet ever-increasing requirements of high-performance products.